Robert G. Chapman

Combinatorial computational method gives new picomolar ligands for a known enzyme.

Combinatorial small molecule growth algorithm was used to design inhibitors for human carbonic anhydrase II. Two enantiomeric candidate molecules were predicted to bind with high potency (with R isomer binding stronger than S), but in two distinct conformations. The experiments verified that computational predictions concerning the binding affinities and the binding modes were correct for both isomers. The designed R isomer is the best-known inhibitor (Kd ∼ 30 pM) of human carbonic anhydrase II.

GUEST DYNAMICS IN CARCEPLEXES : A 2H NMR STUDY

Solid-state 2H NMR powder spectra and T1 longitudinal relaxation data have been collected for carceplexes containing benzene and acetonitrile guest molecules. Analysis of the data suggests that benzene rotates rapidly about its C6 axis with an activation energy of 25.8 ± 0.4 kJ mol–1. In addition, it reorients about the C4 axis of the carceplex cavity with a rate (ca. 106–107 s–1) that is in the intermediate regime on the 2H NMR spectral timescale in the temperature range T= 310–400 K. Lineshape simulations suggest that this reorientation has less than four-fold symmetry owing to unequal site populations, probably a reflection of the deviation from C4 symmetry of the carceplex geometry. Acetonitrile reorients rapidly ( 105 s–1) about a four-fold symmetric axis for T 181 K.

An effective identification and quantification method for Ginkgo biloba flavonol glycosides with targeted evaluation of adulterated products

BACKGROUND Ginkgo biloba L. (Ginkgoaceae) leaf extract is one of the most popular herbal products on the market, as it contains flavone glycosides (≥ 24%) and terpene lactones (≥ 6%), which are proposed to have significant physiological effects. Unfortunately, the challenging financial climate has resulted in a natural health product market containing adulterated ginkgo products. PURPOSE 42 ginkgo samples were analyzed to establish an HPLC profile for authentic ginkgo and common ginkgo adulterants, and to develop a method capable of easily detecting adulteration in ginkgo commercial products. METHOD In this study an efficient and targeted HPLC analysis method was established that is capable of distinguishing flavonol glycosides and aglycones simultaneously for the evaluation of ginkgo powdered extracts (PEs) and finished products in a single, 13 min run. Thirteen ginkgo leaf samples, fifteen standardized powdered extracts, and fourteen commercially available ginkgo products have been analyzed using this new HPLC method. Chromatograms were compared to six standard reference materials: one flavonol glycoside (rutin), three aglycones (quercetin, kaempferol and isorhamnetin), and two isoflavones (genestin and genistein). The quantitative chromatographic data was interpreted by principal component analysis (PCA), which assisted in the detection of unexpected chromatographic features in various adulterated botanical products. RESULTS Only three of the commercially available ginkgo finished products tested in this study were determined to be authentic, with flavonol glycoside rutin, and aglycones quercetin, kaempferol, and isorhamnetin found to be common adulterants in the ginkgo powdered extract and finished product samples. CONCLUSION Despite evidence of adulteration in most of the samples, each of the samples discussed herein met most of the current pharmacopeial standards. It is therefore critical that a preliminary evaluation be utilized to detect adulteration in commercial ginkgo products, prior to the acid hydrolysis procedure utilized in the current testing methods.

An engineered oilseed crop produces oil enriched in two very long chain polyunsaturated fatty acids with potential health-promoting properties

Very long chain polyunsaturated fatty acids (VLCPUFAs) are well recognized for their health benefits in humans and animals. Here we report that identification and characterization of a gene (EhELO1) encoding the first functional ELO type elongase (3-ketoacyl-CoA synthase) in higher plants that is involved in the biosynthesis of two VLCPUFAs docosadienoic acid (DDA, 22:2n-6) and docosatrienoic acid (DTA, 22:3n-3) that possess potential health-promoting properties. Functional analysis of the gene in yeast indicated that this novel enzyme could elongate a wide range of polyunsaturated fatty acids with 18-22 carbons and effectively catalyze the biosynthesis of DDA and DTA by the sequential elongations of linoleic acid and alpha-linolenic acid, respectively. Seed-specific expression of this gene in oilseed crop Brassica carinata showed that the transgenic plants produced the level of DDA and DTA at approximately 30% of the total fatty acids in seeds, and the amount of the two fatty acids remained stable over four generations. The oilseed crop producing a high and sustained level of DDA and DTA provides an opportunity for high value agricultural products for nutritional and medical uses.

Micro-Scale Patterning of Cells and their Environment

Control of the cellular environment is crucial for understanding the behavior of cells and for engineering cellular function. This chapter describes the use of a set of tools in microfabrication called ‘soft lithography’ for patterning the substrate to which cells attach, the location and shape of the areas to which cells are confined, and the fluid environment surrounding the cells, all with micrometer precision. We summarize examples where these tools have helped to control the microenvironment of cells, and have been useful in solving problems in fundamental cell biology. The methods described here are experimentally simple, inexpensive, and well suited for patterning biological materials.